Conventionally, a fuel tank is installed under a floor panel of a car body, forming a part of a rear trunk space or room. However, one of the recent trends in vehicles, and, in particular, in passenger cars, is to lower the position of the floor of the car body. It is, therefore, now often difficult to provide a space for a fuel tank under the floor panel.
One attempt to eliminate this problem is to locate and install a fuel tank above the floor panel of the car body, in a manner designated "saddling installation," between the passenger room and rear trunk room. Such a body structure is known from, for instance, Japanese Unexamined Utility Model Publication No. 61-61227.
In such a saddling installation structure for a fuel tank, an extra or additional member is used to provide a space for the fuel tank. In effect, the fuel tank in the space occupies part of the passenger room. Hence, upon, for instance, a rear-end collision, the fuel tank is pushed into the passenger room as a result of a deformation of the extra or additional member providing the space for the fuel tank. To protect the passengers in the vehicle against injury on the occurrence of a collision, the body structure must be improved.
Body structures of this kind must permit the fuel tank to be removably installed in the fuel tank space from a side of the rear trunk room. Therefore, a worker or mechanic typically must physically climb into the interior of the rear trunk room. Such a fuel tank installation is troublesome and lowers working efficiency in comparison with, for instance, the conventional fuel tank installation.
To improve the efficiency in installing a fuel tank on the car body, it is advantageous to install a fuel tank into a space, open to the underside of the car body, which is formed or provided by a car body floor extending up from the underside of the car body. In this case, the fuel tank is bolted to and supported by a pair of front or rear brackets secured to the car body floor, or otherwise is suspended and supported by a belt.
A space for the fuel tank provided by raising up part of the car body floor, however, lowers the structural rigidity of the car body floor, in particular part of the car body floor where the fuel tank space is provided, in a lengthwise direction of the car body. This local lowering in rigidity causes a deformation of the car body floor upon a rear-end collision, resulting in an easy collapse of the fuel tank.
This kind of deformation may be suppressed to some extent by bolting the fuel tank to the brackets. Although, in this structure, the rigidity of car body floor can be increased by the fuel tank, a larger working space should be left between the fuel tank and the structure surrounding the fuel tank to allow easy bolting of the fuel tank to the brackets. This results in an inefficient use of space of the car body. On the other hand, because a belt is easily deflected due to a deformation of the car body floor during the occurrence of a rear-end collision, suspending and supporting the fuel tank by a belt or belts does not contribute to reinforcing the car body at all, in addition to requiring an inefficient use of space of the car body. For these reasons, neither of these car body structures is desirable for the installation of a fuel tank.